Investigation of joint clearance effects on actuator power consumption in mechanical systems

In this paper, performance analyses of mechanical systems having ideal/non-ideal kinematic joints and pseudo joint (flexural pivot connection) are investigated. A 3D slider-crank mechanism is considered for computational and experimental studies. Power consumption of main actuator is evaluated in case of different clearance sizes, diameters of small flexural pivot and driving speeds. Hertz contact theory comprising the Lankarani and Nikravesh model is considered to describe the contact forces in the clearance joint. In order to overcome the computational drawbacks, a modified Coulomb's friction model is preferred to define the friction effects between matting parts in the clearance joint. Same mechanism models are also used in the experimental stage to measure the real change in the actuator current. Even if the same working parameters are performed, the outputs of this study outline that the clearance in a joint can cause a crucial increase in the current level of actuator. Irregular current fluctuation on actuator can also lead to undesired effects on the actuator lifetime and power consumption. Suitable diameter of the flexural pivot is a solution to decrease the amplitude and peak frequency values of motor currents. Particularly, small pivot diameter can be used as a design variable to decrease the actuator current level at the higher working velocity. This may be an advantage to make the motor lifetime longer, to decrease the power consumption and to prevent the thermal problem in electric motors. (C) 2018 Elsevier Ltd. All rights reserved.